Occasionally I go to my island and bug hunt, but sometimes I attempt the turnips route (mainly just for the badges). I usually forget to buy them, though. When I do remember I usually forget about checking prices. >_<
Even though bug catching can get tedious, I find it quite relaxing.
Mostly I think I make money from selling items and fossils. There actually isn't really much I want to buy anymore because my villagers won't request the PWPs I want!
A combination of all three usually. However, I'm back at home now and my router isn't compatible for me to visit other towns, so I only have beetle farming for now. I'll move to a different place for university in a month, so fingers crossed it works better and I can start selling items and buying turnips!
Beetle farming all the way. I only did turnips to get the badge and then stopped as soon as I got the gold badge. I don't sell villagers/items on the fourm. I might trade but I don't sell, sometimes I even give things away for free.